import type { GitReadResult } from "./git-data.ts";
import { emptyGitStatus } from "./git-data.ts";
import type { PackageVersionReadResult } from "./package-data.ts";
import type { RuntimeReadResult } from "./runtime-data.ts";
import type { FooterState } from "./session-state.ts";

/**
 * Apply a project refresh (git + runtime) onto footer state, preserving
 * last-good values on transient errors and clearing on cwd change / not-a-repo.
 *
 * Returns the cwd to store as `previousCwd` for the next refresh.
 */
export function applyProjectRefreshToState(
  state: FooterState,
  args: {
    cwd: string;
    previousCwd: string | undefined;
    git: GitReadResult;
    runtime: RuntimeReadResult;
    packageVersion?: PackageVersionReadResult;
  },
): string {
  const cwdChanged =
    args.previousCwd !== undefined && args.previousCwd !== args.cwd;

  if (cwdChanged) {
    Object.assign(state, emptyGitStatus());
    state.runtime = undefined;
    state.packageVersion = undefined;
  }

  if (args.git.kind === "ok") {
    Object.assign(state, args.git.status);
  } else if (args.git.kind === "not_a_repo") {
    Object.assign(state, emptyGitStatus());
  }
  // kind === "error": keep previous git fields (unless cwdChanged already cleared)

  if (args.runtime.kind === "ok") {
    state.runtime = args.runtime.runtime;
  } else if (cwdChanged && args.runtime.kind === "error") {
    // Already cleared above; keep undefined.
    state.runtime = undefined;
  }
  // error + same cwd: keep previous runtime

  if (args.packageVersion !== undefined) {
    if (args.packageVersion.kind === "ok") {
      // `null` means "no manifest in this cwd"; clear so the segment disappears
      // even on the same cwd when the user removes their manifest.
      state.packageVersion = args.packageVersion.result ?? undefined;
    } else if (!cwdChanged) {
      // error + same cwd: keep previous packageVersion (last-good semantics)
    } else {
      state.packageVersion = undefined;
    }
  }

  return args.cwd;
}